Presidential prediction 2012 – final

November 6th, 2012, 2:00pm by Sam Wang

I apologize to all for the late update. We wanted to make sure all the polls were in. And it’s a hectic day.

The following are final estimates, based on taking polling data over longer intervals than our usual 1-week rule. Instead, I found the period over which a state’s polling variance was minimized, as a means of identifying stability.

ELECTORAL PREDICTION (mode): Barack Obama 303 EV, Mitt Romney 235 EV. The mode is the single most frequent value on the EV histogram. It corresponds to the map below, and has a 22% chance of being exactly correct. The next-most-likely outcome is Obama 332, Romney 206 EV.

ELECTORAL PREDICTION (median): Obama 305 EV, Romney 233 EV, Popular Vote Meta-Margin Obama +2.76%. This median is almost guaranteed to be off, since 305 EV is not a common combination. It is the midpoint of all possibilities, and reflects the overall shape of the distribution. The nominal 1-sigma band is Obama [293, 332] EV.

TWO-CANDIDATE POPULAR VOTE SHARE: Obama 51.1%, Romney 48.9%.

ALL-STATE PREDICTION (binary outcomes):

As I wrote late last night, Florida is a hard case. Several new polls came out this morning, making the median basically zero. As a tie-breaker I resorted to mean-based statistics. I will be unsurprised for it to go either way. Nate Silver and Drew Linzer went the other way. We are all tossing coins. I am prepared to lose the coin toss.

In Florida, a recount is triggered by a margin of 0.5% or less (recount rules, Brennan Center for Justice). I estimate that there is a 50-50 chance of a recount. We might not know the exact outcome for some time.

The next-closest state is North Carolina, with margin of Romney +1.0%. All other margins are 2% or greater.

POPULAR VOTE. Using the above Meta-Margin for the last three days was Obama +2.76%. The median of national polls is Obama +1.0 +/- 0.4% (n=21 polls). The approach I described before for combining these measures gives

Final predicted popular-vote margin: Obama +2.2 +/- 1.0%.

Two-candidate vote share: Obama 51.1%, Romney 48.9%.

Allowing 1% for minor-party candidates: Obama 50.6%, Romney 48.4%.

Finally, here is the EV histogram based on the optimized probabilities. The two highest peaks correspond to FL-Romney and FL-Obama.

By 5:00pm I’ll have some graphs for you to print. They will let you compare the returns with polls.

I love your site. I sincerely hope that all of the many models that I have seen for Obama hold true for tonight within the next few hours as the returns come in. Though it is anecdotal, I can confirm that there has been a record turnout in Northern Virginia—at least at my polling place—compared to 2008. I arrived at 5:20am this morning and didn’t get out until roughly 7am. Though this is an aside, I feel that the latino vote is going to be surprisingly abundant this year. I spoke to one girl in line with me who registered herself along with her 34 family members for this election. They were particularly driven by Romney’s “self deport” comments. These responses along with Obama’s excellent “Romney?? No!!” commercials on Univision and Telemundo may have created a goundswell.

Driving the Republican party to the left is not a bad thing at all. I doubt the tea party follows because the press they have gotten makes them ‘full of themselves’. Personally, I’d love to see the Tea Party make an independent go of it in 2016. I hope the Latino vote is much stronger than expected and breaks Democrat and splitting the right next cycle.

Adding my thanks, Dr. Wang, for your efforts to educate us while informing while motivating so many to play a more active role in the preservation of what remains of our democracy.

I understand your reasoning, and applaud your mature quantitative equanimity, but still hope Florida falls to the blue column when all the inevitable legal wrangling is finally over. Though not yet a US citizen, my wife has been tirelessly helping us down here with GOTV for the President, while keeping a small but intense spotlight on us for her online students in Japan. Mr. Obama is beloved by the great majority of non-Americans in the world, and it will bring great sadness to them, and to her, if we cannot deliver Florida for him tonight.

@ Steven S:

As to your item 2), a very useful and timely question!

You are right that Dr. Wang and his several colleagues are a beacon lighting the way to scientifically-based understanding of the great issues facing us.

Of the several candidate issue areas where numbers-driven analysis can have a major impact on the public consciousness, a lifetime in quantitative analysis persuaded me a few years ago that the most fruitful is surely climate change. In one sentence, those of us with the scientific, engineering, quantitative, and industrial experience to realize the highly probable scale of the disaster that is even now beginning to confront our species, and the thousands of others we share the planet with, have pretty miserably failed to, as Dr. Wang is doing, educate, inform and motivate humans to take responsibility for the carbon-based energy we extract and mostly waste.

A second and very much related issue area where numbers are sorely missing, or have been veiled by corporate and other interests, is in the relative costs and benefits, risks and rewards, of genetically-modified foods. Faced as the will be with food shortages beyond anything we can imagine now, our grandchildren will curse this present generation for failing to find safe, economically-viable sources of basic foodstuffs.

A third and also survival-related area is global over fishing, marine acidification, and destruction of the marine food chain.

This not the place to argue my allegations; my email is above.

But be aware: for all the lack of attention and effective communication by quantitatively qualified professionals in these and other life-and-death areas of investigation, there are a surfeit of “quant” talents working in “data mining”, “inferential online search”, and “website navigation tracking.”

So, we have the folks who have the smarts and skills. It’s just that figuring out how to help advertisers sell more crap to our kids pays waaaay better than trying to persuade their parents to change our unsustainable economic behavior.

I do wish that we respect the work that Dr. Wang has done for us and thus respect his dislike for gambling. So, please, no bragging or sob stories about your bets. Personally, I think if you are good at Math there are far more enjoyable ways to spend one’s time than gambling. I do, however, look at intrade odds everyday; and plan to look at them, especially now before the poll closings. This because, their movement will tell me, more or less, what is happening.

You yanks so often seem alien to us – Romney wouldn’t get 10% of the vote in the UK and most of Obama’s attack ads would be despised – that it’s a great joy and comfort to come across a bright evidence based site like this. Thanks Sam and crew, thanks half dead cat posters, keep up the good work. Oh, and I’m also for 319.

MATH QUESTION: as per Huffpo’s 100 reporting FL totals, Obama got 49.8596% and Romney 49.2949%, so Obama won by 0.5558, technically more than .5%. Does that mean no recount? Is there some bit of nastiness with the 3rd party votes changing the way the .5% is calculated?

Has anyone done (or seen) a county-by county map with the county sizes distorted by the size of the electorate in each county, a la PEC’s state map ? I know, you might not be able to recognize a lot of the states given the distribution of vote margins.